It is well known that UDP-glucose is a direct substrate in cellulose biosynthesis of Acetobacter, which is linked together by a membrane protein complex called "cellulose synthase", and released out of cells. This complex has been reported to consist of four proteins encoded by an operon of cellulose synthase gene, being named bcs A, B, C and D, respectively (H. C. Wong, et al., P.N.A.S., Vol.87, pgs.8130-8134 (1990)). Among these genes, bcsA, B and C genes are known to be essential for cellulose synthesis since their destruction would lose cellulose-producing capacity. It has been reported that bcsd gene also plays an important role since its destruction would cause a significant change of the structure of cellulose (I. M. Saxena, et al., J.Bacteriol., Vol.176, pgs.5735-5752 (1994)). Recently, it has been reported that the second cellulose synthase gene operon was obtained (I. M. Saxena, et al., J.Bacteriol., Vol.177, pgs.5276-5283 (1995)).
The cellulose synthase complex needs di-GMP as a cofactor. di-GMP is synthesized by cyclase and a gene encoding this enzyme has also been reported (R. Tal and D. H. Gelfand, PCT WO93/11244 (1994)).
It has been reported that upstream of the cellulose synthase gene operon, there are a cellulase gene(CMCase) and another gene (R. Standal, et al., J. Bacteriol., Vol.176, pgs.665-672 (1994)).
The present inventors have studied the cellulose synthase complex gene operon of Actobacter, and now succeeded in determinating the base sequences of a series of genes comprising a novel cellulose synthase complex gene operon and cellulase gene, which originate in Acetobacter xylinum subsp. sucrofermentans. According to our examination of the base sequence of a novel gene downstream of the novel cellulose synthase complex gene operon, we have also found that the nobel gene conserves well the sequence/region that are maintained in .beta.-glucosidase of various organisms (Y. Kashiwagi, et al., J.Ferment.Bioeng., Vol.78, pgs.394-398 (1994)) and therefore confirmed that this gene is .beta.-glucosidase.
Further, we have actually purified a protein encoded by the above .beta.-glucosidase gene, and examined its various properties.